The present invention relates to intraocular lenses (IOLs). More particularly, the invention relates to IOLs with one or more translational zones which are adapted to provide accommodation in the eye.
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag, containing a crystalline lens, a ciliary muscle, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focusing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL has very limited, if any, accommodating ability. However, the wearer of such an IOL continues to require the ability to view both near and far (distant) objects. Corrective spectacles may be employed as a useful solution. Recently, multifocal IOLs without accommodating movement have been used to provide near/far vision correction.
Attempts have been made to provide IOLs with accommodating movement along the optical axis of the eye as an alternative to shape changing. Examples of such attempts are set forth in Levy U.S. Pat. No. 4,409,691 and several patents to Cumming, including U.S. Pat. Nos. 5,674,282 and 5,496,366. The disclosure of each of these patents is incorporated herein by reference. One problem that exists with such IOLs is that they often cannot move sufficiently to obtain the desired accommodation.
It would be advantageous to provide IOLs adapted for accommodating movement which can achieve an increased amount of accommodation.
New accommodating IOLs have been discovered. The present accommodating IOLs take advantage of employing an optic made of two different materials to enhance the accommodation achievable in the eye in response to normal accommodative stimuli. Thus, the present lenses provide for controlled vision correction or focusing for both near objects and far or distant objects. Further, a greater overall range of accommodation is often achieved. The present IOLs are relatively straightforward in construction and to manufacture or produce, can be implanted or inserted into the eye using systems and procedures which are well known in the art and function effectively with little or no additional treatments or medications being required.
In one broad aspect of the present invention, intraocular lenses (IOLs) are provided and comprise an optic adapted to focus light toward a retina of a mammalian eye and, in cooperation with the mammalian eye, to provide accommodation. The optic includes a first lens portion adapted to move in response to the action of the mammalian eye; and a second lens portion secured to the first portion of the optic and having a higher refractive index than the first portion and/or being positioned generally anterior of the first portion. The first lens portion is comprised of an optically clear material that is easily reshaped and/or is axially movable when exposed to force exerted by the mammalian eye.
In one embodiment, the second lens portion of the optic is comprised of an optically clear material having a higher refractive index than the first lens portion. For example, the first portion may have a refractive index of about 1.37 or less, while the second portion preferably has a refractive index of at least about 1.42. The difference in refractive index between the first and second portions preferably is in the range of at least 0.03 and more preferably is in the range of about 0.04 to about 0.1 or more. The second portion of the optic preferably is positioned generally anterior of the first portion. More preferably, the second portion includes an anterior surface which defines at least a portion of the anterior face of the optic.
The second lens portion may be reshapable by the force exerted on the optic by the eye or may be substantially rigid in response to such force. As a result of this, potential materials of construction for the second portion may vary significantly.
The present lenses very effectively provide for both enhanced movement, for example, reshaping and/or axial movement, because of the substantially compliant or deformable first lens portion, while, at the same time, providing for relatively high refractive index and therefore effective corrective optical powers with a reduced sized lens because of the higher refractive index second lens portion. This combination of enhanced movement and high refractive index provides a substantial benefit in achieving accommodation in the mammalian eye.
In one very useful embodiment, the first lens portion of the optic is adapted to be reshaped in response to the action of the mammalian eye. Alternately, or in conjunction with the reshaping of the first portion, this first portion may be adapted to move axially in the mammalian eye in response to the action of the mammalian eye.
To achieve further enhanced accommodation, the optic preferably further comprises a third lens portion spaced apart from the second lens portion, secured to the first lens portion, and having a higher refractive index than the first portion, more preferably substantially the same refractive index as the second portion, and/or positioned generally posterior of the first portion. Advantageously, the second and third portions are located so that their central axes are aligned with the optical axis of the optic. Looked at from another perspective, the second portion may be considered as an anterior lens portion while the third portion may be considered a posterior lens portion. The first portion preferably is situated between the second and third portions.
The embodiment of the present IOLs with the optic including second and spaced apart third lens portions is advantageous in that the optic is still responsive to the force exerted by the eye on the optic while, at the same time, the positioning and/or refractive indexes and/or optical powers of the second and third portions provide for obtaining enhanced accommodation with such an optic. The second lens portion, for example, the anterior lens portion, may have a higher, preferably positive, optical power than the third lens portion, for example, the posterior lens portion. In other words, the second lens portion can have a positive optical power relative to the baseline optical power, which is the optical power for distance vision correction, and the third lens portion can have a negative optical power relative to the baseline optical power. The use of lens portions with positive and negative optical powers, for example, highly positive and highly negative optical powers, extends the total accommodative dioptic change beyond that of the movement of a single lens design. Such positive/negative lens portions including a relatively easily deformable first portion provide a larger dioptic power change relative to a single lens design based on the same amount of movement of the lens in the eye. Thus, increased or enhanced amounts of accommodation are provided using the present optics including positive and negative lens portions.
As noted previously, the second and third lens portions of the optic may have substantially the same refractive index. More preferably, the second and third portions of the optic are made of substantially the same material, that is material having substantially the same chemical makeup. The refractive index of each of the second portion and the third portion of the optic preferably is at least about 1.42.
The reshaping or deformation of the first lens portion can cause an axial movement of the first portion which imparts an axial movement of the second lens portion, or the second and/or third portions of the optic. Axial movement of the second portion or the second and/or third portions of the optic have a relatively large effect on the accommodative power of the optic. Thus, providing axial movement of the second portion, or the second and/or third portions of the optic is one important feature of the present invention. Of course, reshaping of the first portion in and of itself may provide accommodative power. The overall accommodative power of the optic in accordance with the present invention preferably is increased beyond the accommodation obtained by the axial movement of a single lens of uniform composition, for example, because of the reshaping or deformation of the first portion and/or the presence of the third portion.
In another very useful embodiment, a force transfer assembly is provided. This force transfer assembly has a first end coupled to the optic and a second end extending away from the optic and adapted to contact a posterior bag of the mammalian eye when the IOL is located in the mammalian eye. The force transfer assembly is adapted to transfer the force exerted by the eye to the optic to facilitate the movement of the optic. Preferably, the force transfer assembly is adapted to transfer the force exerted by the eye to the optic to facilitate at least one of reshaping the first portion in response to the action of the mammalian eye and moving the first portion axially in the mammalian eye in response to the action of the mammalian eye. In a very useful embodiment, the force transfer assembly is adapted to transfer force from the eye to the optic to both facilitate reshaping of the optic and moving the optic, for example, at least a portion of the optic, axially in the eye. The force transfer assembly is very effective in facilitating the accommodation obtained by the present IOLs.
However, it should be noted that such force transfer assembly is not essential in accordance with the present invention. The optic can be sized and configured to fit within the capsular bag and to contact the capsular bag, in particular the periphery of the capsular bag, so that the force exerted by the eye can be transferred directly to the optic of the present IOL. Such IOLs in which the optics are sized and configured to contact the peripheral capsular bag are very effective in being reshaped to provide the desired accommodation. In addition, substantially filling the capsular bag volume with a deformable optic including a first portion and a second portion and possibly a third portion as in the present optics, reduces the risk of decentration or tilt of the lens system in the eye, as well as reducing the risk of decentration or tilt between individual lens components, relative to lens systems in which the optic does not substantially fill the capsular bag volume. Providing for a reduced risk of decentration is highly advantageous, for example, as the capsular bag contracts. Even if the contraction of the capsular bag is asymmetric, for example, because the zonules are not of uniform strength, the elastic properties of the first portion mitigate against this asymmetry and reduce the risk of decentration.
Substantially filling the capsular bag volume, as described above, may reduce the risk of posterior capsular opacification (PCO) particularly if the posterior surface or face of the optic remains in contact with the posterior wall of the capsular bag during all states of accommodation.
In a very useful embodiment, the present IOLs are deformable for insertion into the mammalian eye through a relatively small incision, for example on the order of about 3.5 mm or less. Thus, both the first and second portions of the optic, and the third portion of the optics and/or the force transfer assembly, if present, are all deformable for insertion through a small incision into the eye. Such IOLs regain their original undeformed condition rapidly after being inserted into the mammalian eye.
In order to facilitate the movement in the eye, the first portion preferably is more deformable than the second portion and the third portion, if present, of the present IOLs. As noted previously, the second portion, and the third portion, if present, can be substantially rigid, for example, in response to forces exerted by the eye. However, it is preferred that the entire IOL be sufficiently deformable to be passed through an incision in the eye which is less than the diameter of the IOL in its undeformed condition.
The present optics may be made of any suitable materials of construction. For example, the present optics may be made of one or more polymeric materials employing techniques used in manufacturing conventional polymeric material IOLs. Examples of the materials from which the present optics can be made include, without limitation, acrylic polymeric materials, silicone polymeric materials, and the like and combinations thereof. Although combinations of different polymeric materials may be employed, the present optics preferably are made of different polymeric materials of the same general chemical family. For example, the first portion of the IOL may be made of one silicone polymeric material while the second portion and third portion, if present, are made of a different silicone polymeric material. Similarly, the first portion of the optic can be made of one acrylic polymeric material while the second portion and third portion, if present, are made of a different acrylic polymeric material. In any event, the first portion of the present optics and the second portion and third portion, if present, preferably are made of compatible materials of construction, that is materials which can be used to produce an effective IOL which remains as an intact structure in the eye without significant deterioration for periods of time extending for at least about 20 or about 25 years or more.
In one embodiment, the first lens portion of the present optics is made of a very low modulus silicone polymeric material, while the second lens portion and third lens portion, if present, are made of a higher refractive index silicone. To illustrate, the first portion of the optic can be composed of a silicone polymeric elastomer with the following material properties:
Optically clear;
Refractive index of at least about 1.37;
Shore A hardness of about 0; and
At least about 1000% elastic elongation.
The second lens portion, and third lens portion, if present, of the present optics can be made of a different silicone elastomer with the following material properties:
Optically clear;
Refractive index of about 1.42 or higher;
Shore A hardness in a range of about 0 to about 30; and
An elastic elongation higher than about 150%, preferably in a range of about 150% to about 400%.
The second lens portion and third lens portion, if present, can be made of widely varying materials. Examples include, without limitation, rigid and foldable acrylic polymeric materials, rigid and foldable non-acrylic polymeric materials, deformable or foldable silicone polymeric materials and the like and combinations thereof. The second portion and third portion, if present, can be hydrophobic or hydrophilic.
Many materials which meet the above-noted criteria are conventional and well known in the art. Therefore, a detailed description of such compositions is not presented here.
However, by way of illustration, the following materials of construction, based on constituent monomeric components, is presented.
The present optics are conveniently produced using conventional and well known techniques, such as molding techniques. In one embodiment, the second portion, and third portion, if present, are produced in a separate mold and then inserted into a mold into which is placed the monomeric or partially polymerized monomeric mixture of the first portion precursors. The combination is then heated to elevated temperatures, for example on the order of about 40xc2x0 C. to about 100xc2x0 C., and/or subjected to ultraviolet radiation and the composition combination is allowed to cure, preferably for about one hour to about 24 hours. The material in the mold is then post-cured, preferably at a temperature in the range of about 70xc2x0 C. to about 130xc2x0 C., and/or by being subjected to ultraviolet radiation for a period of time, preferably for about two hours to about 30 hours. After curing (and post-curing), the mold is disassembled and the molded lens body recovered.
The force transfer assembly, if present, can be made or provided separately and then coupled to the optic or lens body, for example, in a mold in which the optic is cured or post-cured. Alternately, the force transfer assembly can be coupled to the lens body after the lens body is formed. Conventional techniques can be employed. For example, one or more recesses can be formed in the optic and the force transfer assembly can be secured to the optic by having an end placed in the recess, for example, in much the same manner in which a haptic or fixation member is secured to the optic of a conventional IOL.
Any suitable material or combination of materials of construction may be utilized in the force transfer assembly and the force transfer assembly can have any suitable configuration provided that such assembly is effective to at least partially transfer the force of the eye to the optic of the IOL. The force transfer assembly preferably is more rigid or less flexible than the first portion of the optic. However, the force transfer assembly preferably is sufficiently deformable to be folded or otherwise deformed to pass through a small incision for insertion into the eye. The force transfer assembly can be a single member substantially surrounding the optic, or can be a plurality, for example, about 2 or about 3 to about 4 or about 6, individual elements positioned around the peripheral edge of the optic. Although the force transfer assembly can include at least one hinge to facilitate axial movement of the optic in response to the action of the eye, preferably the force transfer assembly does not include a hinge.
The force transfer assembly preferably is made of a material or materials which are compatible with the eye and with the other material or materials included in the IOL. Examples of materials which can be included in the present force transfer assemblies include, but are not limited to, polypropylene, silicone polymeric materials, acrylic polymeric materials including but not limited to polymethylmethacrylate (PMMA), polyamides and the like and combinations thereof.
In a further broad aspect of the present invention, methods for inserting an IOL in an eye are provided. Such methods comprise providing an IOL in accordance with the present invention, as described herein. The IOL is placed into the eye, for example in the capsular bag of the eye, using equipment and techniques which are conventional and well known in the art. The IOL is placed in the eye so that the eye effectively cooperates with the IOL to provide accommodation as desired. After the IOL is inserted into the eye, any incision in the eye is closed. After a relatively short period of recuperation, the IOL provides the wearer of the IOL with substantially effective accommodation. No further treatments or medications, for example, to paralyze the ciliary muscle, to facilitate fibrosis or otherwise influence the position of the IOL in the eye, are required. Preferably the optic is deformed prior to being placed into the eye. Once the IOL is placed in the eye, and after a normal period of recovery from the surgical procedure, the IOL, in cooperation with the eye, provides the mammal or human wearing the IOL with the desired accommodation.
Any and all features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combinations are not mutually inconsistent.